One aspect relates to a device comprising a hollow body, an inner volume and a surrounding volume, wherein the hollow body comprises a cermet electrode; to a method for producing a device, comprising the method step of connecting a housing to a cermet electrode; a device obtainable by a method comprising the method step of connecting a housing to a cermet electrode; and to a use of a cermet electrode for producing a wireless cardiac pacemaker.
Electrical stimulation of human or animal tissue for therapeutic purposes has long been known in the art. For therapy of this kind, a device providing electrical pulses can be implanted in a human or animal body to be treated. Examples of implantable devices that provide electrical pulses are pacemakers and defibrillators. Pacemakers known in the prior art are bladder pacemakers, diaphragm pacemakers, intestinal pacemakers, respiratory pacemakers, brain pacemakers and cardiac pacemakers. Implantable cardiac pacemakers that have long been known in the art typically comprise a control unit, which is connected to a measuring unit and to an electrical pulse generator. The measuring unit detects electrical potentials of the heart via attached electrodes. The electrical pulse generator delivers electrical stimulation pulses to cardiac muscle tissue via attached electrodes. Conventional cardiac pacemakers that have long been known in the art are implanted at some distance from the heart, for example below the collarbone in humans. From the measuring unit contained in the housing and from the electrical pulse generator, flexible electrode lines are routed into a heart chamber. There, the electrode lines end at electrodes which transmit the electrical stimulation pulses to the cardiac muscle tissue. The control unit is powered via a likewise implanted battery. The likewise implanted battery can be contained in the housing or can be connected to the latter by a plug-socket connection. Numerous refinements of such cardiac pacemakers concern the materials used, the programming of the control unit, and the power supply. Cardiac pacemakers presently known in the art do not comprise the flexible electrode lines between the measuring unit and electrodes and between the electrical pulse generator and electrodes. Instead, the housing is designed such that it comprises the electrodes on its outer sides. By suitable dimensioning of such a cardiac pacemaker, it can be implanted in a heart, where the electrodes are in contact with cardiac muscle tissue. Persons skilled in the art refer to cardiac pacemakers of this kind as wireless cardiac pacemakers. A wireless cardiac pacemaker of this kind is disclosed in EP 1 714 670 A1. A wireless cardiac pacemaker comprises at least two electrodes. One electrode is formed as a cathode, and a further electrode is formed as an anode. The cathode is often designed as a tip electrode and the anode as a ring electrode. The cathode serves to stimulate the cardiac muscle, and the anode serves to measure heart activity. The housing, which is made of titanium, is customarily used as the anode. The cathode is normally formed by a contact body and a feed-through wire. The contact body is designed to contact the tissue that is to be stimulated. The contact body is normally made of a platinum-iridium alloy and is produced by machining. The feed-through wire is welded onto the contact body and establishes an electrical connection between the electronics inside the housing and the contact body. As regards the implantability of the cardiac pacemaker, it is of great importance that the electrical feed-through is hermetically sealed. To achieve this, the feed-through wire normally runs through a ceramic ring, to which the feed-through wire is soldered by a gold solder. The ceramic ring in turn is soldered into a metal flange, which is flanged onto the housing by welding.
The wireless cardiac pacemakers of the prior art have at least the following disadvantages. An electrode consists of several parts, at least the contact body and the feed-through wire. These parts have to be connected in at least one work step. This work step makes a method for producing a wireless cardiac pacemaker of the prior art more expensive or more laborious, or both. An electrode of a wireless cardiac pacemaker of the prior art is constructed in several pieces. This increases the electrical resistance compared to a one-piece electrode, and this increases the power consumption of a wireless cardiac pacemaker of the prior art. The increased power consumption shortens the battery life of a wireless cardiac pacemaker of the prior art. This shortens the time between necessary surgical interventions in the organism in which the wireless cardiac pacemaker of the prior art is implanted. The connection between the parts of the electrode of the wireless cardiac pacemaker of the prior art may come loose, which can adversely affect the function of the wireless cardiac pacemaker or can damage the organism in which the wireless cardiac pacemaker is implanted. Moreover, the feed-through wire has to be connected to the ceramic ring in an additional work step. This work step too makes a method for producing a wireless cardiac pacemaker of the prior art more expensive or more laborious, or both. In the prior art, the connecting of the feed-through wire to the ceramic ring is effected by soldering with a gold solder. The use of the gold solder makes the method for producing a wireless cardiac pacemaker of the prior art more expensive. The connection of the ceramic ring to the feed-through wire of wireless cardiac pacemaker of the prior art may also come loose, which can adversely affect the function of the wireless cardiac pacemaker or can damage the organism in which the wireless cardiac pacemaker is implanted. Moreover, the connection of the ceramic ring to the feed-through wire is a potential source of leakage of the wireless cardiac pacemaker of the prior art. Furthermore, the production of a contact body of a wireless cardiac pacemaker of the prior art is laborious or expensive, or both. It is advantageous to minimize the outer (macroscopic) surface of the contact body which, for stimulation purposes, is brought into electrically conductive contact with the cardiac muscle tissue. On the other hand, the outer surface area of the contact body in mechanical contact with the cardiac muscle tissue should not be so small that the electrode perforates the cardiac muscle tissue. Accordingly, in the prior art, the surface of the contact body brought into contact with the cardiac muscle tissue is provided with a partially electrically insulating coating, for example with Parylene. Such coating adds a further work step to a method for producing a wireless cardiac pacemaker of the prior art. Such a work step makes a method for producing a wireless cardiac pacemaker of the prior art more expensive or more laborious, or both. Moreover, such a coating or parts of such a coating may come loose, which can adversely affect the function of the wireless cardiac pacemaker or can damage the organism in which the wireless cardiac pacemaker is implanted. Furthermore, if the inner (microscopic) surface of the contact body coming into contact with the cardiac muscle tissue is as large as possible, this affords advantages as regards operating a wireless cardiac pacemaker. In the prior art, this surface is therefore sintered or coated, or both. As regards a method for producing a wireless cardiac pacemaker, this adds further work steps that are laborious or expensive, or both. Moreover, such a coating or parts of such a coating may also come loose, which can adversely affect the function of the wireless cardiac pacemaker or can damage the organism in which the wireless cardiac pacemaker is implanted. In a wireless cardiac pacemaker of the prior art, the housing is used as the anode. It is advantageous to increase an inner (microscopic) surface of a part of the housing. In the prior art, this is done by sintering or coating, or both. As regards a method for producing a wireless cardiac pacemaker, this adds further work steps that are laborious or expensive, or both. Moreover, such a coating or parts of such a coating may also come loose, which can adversely affect the function of the wireless cardiac pacemaker or can damage the organism in which the wireless cardiac pacemaker is implanted. Moreover, the use of the housing as the anode makes it difficult to fix electronics in the housing without causing an electrical short circuit with the housing. Since the anode is the entire housing, a measurement of the heart activity is easily affected by interference signals. If electrical stimulation or a measurement of electrical potentials is to take place separately at different points of cardiac muscle tissue that lie close to each other, it is advantageous to arrange a plurality of electrodes close together. With electrodes of wireless cardiac pacemakers of the prior art, such an arrangement is impossible, or it is possible only at great expense. A fundamental problem when it comes to implanting wireless cardiac pacemakers is that of inflammation. Steroidal anti-inflammatories can be used to counter the occurrence of inflammation caused by the implanted wireless cardiac pacemaker. In the prior art, these anti-inflammatories are introduced into a bore in an electrode of the wireless cardiac pacemaker. A multiplicity of such bores containing steroidal anti-inflammatories would be advantageous. Producing a multiplicity of bores in an electrode of a wireless cardiac pacemaker of the prior art is very laborious.